The present invention relates generally to a belt sander, and more particularly to a belt adjusting device of the belt sander.
The conventional sanding machine comprises a machine base which is provided at both ends with a driving roller pivoted thereto, and a driven roller pivoted thereto. A sanding belt is fitted with the outer edges of these two rollers. The driving roller is driven by a motor to actuate the sanding belt to move. A workpiece to be finished is brought to make contact with the sanding belt in motion such that the workpiece must be moved around from time to time to prevent the surface of the sanding belt from being worn out unevenly, thereby prolonging the service life span of the sanding belt. In addition, the prolonged contact of the workpiece with a constant point of the sanding belt can result in the burning of the workpiece.
It is the primary objective of the present invention to provide a belt sander with a belt adjusting device enabling the sanding belt to be adjusted leftwards and rightwards, so as to alleviate the work load of an operator.
It is another objective of the present invention to provide a belt sander with a belt adjusting device which is provided with means to adjust automatically the displacement of the sanding belt so as to change the contact position between a workpiece and the sanding belt, thereby preventing a local burning of the workpiece.
It is still another objective of the present invention to provide a belt sander with a belt adjusting device enabling the sanding belt to be put to use uniformly, so as to prolong the service life span of the sanding belt.
In keeping with the principle of the present invention, the foregoing objectives of the present invention are attained by the belt adjusting device, which comprises a seat, a sanding belt, a reduction gear set, a swiveling member, and an action rod. The seat is provided respectively at both ends thereof with a driving roller and a driven roller. The driving roller is driven by a motor. The driven roller is mounted at one end on the seat. Both the driving roller and the driven roller have a free end. The sanding belt is movably fitted with the outer edges of the two rollers. The reduction gear set is mounted on the free end of the driving roller and is formed of a plurality of reduction gears and a shaft rod. The shaft rod is actuated to turn by the reduction gears which are driven by the motor. The swiveling member is provided at one end with a long slot, and at other end thereof with a push portion. The shaft rod is pivotally put through the long slot such that the shaft rod slides in the long slot so as to enable the push portion to swivel in a predetermined angle. The action rod is movably disposed at one side of the seat such that the action rod is capable of a left horizontal displacement and a right horizontal displacement. The action rod is pivotally fastened at one end with the free end of the driven roller such that other end of the action rod is in a constant contact with the push portion of the swiveling member. As the action rod is pushed by the push portion to slide, the free end of the driven roller is pushed by the action rod to displace up and down. The sanding belt can be thus moved on the two rollers to facilitate the adjusting of the contact position of the sanding belt in relation to a workpiece.